1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member including a photoconductive layer which is composed chiefly of amorphous silicon.
2. Description of the Prior Art
Electrophotographic photosensitive members which are composed chiefly of amorphous silicon are disclosed, for example, in U.S. Pat. Nos. 4,394,426, 4,359,514, 4,414,319, 4,418,132, 4,423,133, 4,771,042, etc. Such photosensitive members have various advantages over those composed chiefly of selenium or cadmium sulfide in that they have higher resistance to heat and abrasion, are harmless and have higher photosensitivity. Furthermore these members have the advantage that they are usable for copying machines and intelligent copying machines including a laser printer because of sufficient sensitivity to light of long wavelengths.
When amorphous silicon is used for electrophotographic photosensitive members, the photoconductive layer formed on the substrate must have a sufficient thickness so as to have a high dark resistivity and to obtain the amount of charge required for the developing process. The photosensitive member has a surface layer for preventing the flow of surface charges from the surface of the member into the photoconductive layer. The surface layer is made of a material composed chiefly of amorphous silicon and containing nitrogen, carbon or oxygen.
However, the photoconductive layer when it has sufficient thickness, tends to release or peel from the substrate so that the electrophotographic photosensitive member comprising the photoconductive layer has insufficient in its durability for use. Larger thickness of the photoconductive layer result in higher releasability or peelability.